Limiting reactance-coil.



1. .F. PETERS. LIMITING REACTANCE COIL.

Patented Oct. 2,1917.

2 SHEETS-SHEET I.

WITNESSES: v

NVENTUR ATTORNEY I. F. PETERS. UMITING REACTANCE COIL. APPLICATION FILED m3. 5. 19m.

Patented Oct. 2,1911

2 SHETSSHEET 2 F/f I mvsmoa ATTORNEY UNITED STATES OFFICE.

JOHN F. PETERS, OF PITTSBURGH. PENNSYLVANIA. ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

LIMITING REACTANCE-COIL.

Application filed February 5 1914.

To all whom it may concern:

Be it known that I, JOHN F. PETERS, a citizen of the United States. and a resident of Pittsburgh. in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Limiting Reactance-(loils, of which the following is a specification.

y invention relates to curi'ent liniiting reactances, and it has particular reference to improvements in cu rrentl i m i tin g reacta n ces which are inserted in power circuits as pro tective means for the generating equipment of a power station.

In power generating systems. it is of utmost importance that the service rendered be uninterrupted, and that the power-generating apparatus be circuits. disturbances, etc, in order to insure reliability of operation. 'ith the development of power stations having large capacity units embodied therein, it is particularly desirable to protect each of the gen erators from severe strains occasioned by short circuits, and to limit the possible local concentration of power at such occurrences.

When a short circuit occurs upon one of the feeders or distributing lines of a power system, each of the generatois supplying power to the main feeder buses is required to furnish momentarily an abnormal load until the circuit breakers associated with the affected feeder have had time to open and thereby disconnect it from the buses, or until the speed of the generators has sufiicicntly decreased to prevent further current flow of an abnormal value.

Inasmuch as large-capacity high-speed turbo alternators are the usual type of electrical power generators in modern stations, severe damage may result to these generators on the occurrence of a short circuit because i of their ability to maintain a high speed for an appreciable time under severe loads and because of their low internal reactance. A

momentary short circuit current of 30 to- 40 times full load current is not uncom men, and such quantities of current flowing in the .windings of the generator may cause serious distortion and displacement of the coils. In'order to limit the value of the current to an a mount that will not damage the generator or seriously atiect the continuity oi service, a reactance is inserted in the circuit. This Specification of Letters Patent.

protected against short 'dinally extending tie rods 6 Patented Oct. 2, 191 7. Serial No. 816.717.

reactant-e may be inserted by adding an external power limiting reuctance or by so designing the generator as to increase its self-inductive rcactance, or by coinbining both of the above-mentioned means of increasing the reactancc. My invent-ion refers only to a power-limiting reactancc that is external to the generator to which it affords protection.

One object of my invention is to furnish a powenlimiting rcactance which will successfully resist severe strains and be inexpensive to construct.

Another object of my invention is to provide a power-limiting reuctance which will admit of thorough self ventilation of the coils comprising the same.

A further object of my invention is to design a power-limiting reactance which will have internal losses of a small value only, and which will be efiicient in its operation.

In order to understand my invention more fully, reference may be had to the following description and the accompanying drawing, in which Figure 1 is a side View, partially in section, of a reactance coil constructed in accordance witlr my invention; Fig. 2 is a plan view of one of the coil-sections of my reactance coil; Fig. 3 is a plan view of another one of the coil-sections which is immediatelv adjacent to the coil-section shown in Fig. 2. Fig. 4 is a view in development of another reactance coil which embodies my invention; Fig. 5 is a plan view of the coil of Fig. 4 in which the coil connections between adjacent and concentric coil layers are 1 shown; Fig. 6 is a partial and cross sectional view showing the method of construction of the coil of Fig. 4; Fig. 7 is a diagrammatic representation of a distributing system embodying power-limiting reactance coils; and Fig. 8 is a diagrammatic view of another distributing system in which the power-limiting reactance coils are inserted to aflordprotection to generators.

Referring to Figs. 1 and 2, the reactance coil 1 of my invention comprises a plurality of flat spiral coil sections 2 which are disposed one above another. Conductors 3 of each coil section are received in recesses or notches 4 formed in radial bars 5. Longituengage the re- ](tll] g portions 7 of the bars to rigidly Fold the coil sections 3 in fixed positions. Binding posts 8, mounted upon the top and bottom frames 8", furnish proper means to effect electrical connections between the coil 1 and the desired sections of a conductor of the distributing system. Insulating supports 9, comprising porcelain insulators 10 and feet 11 associated therewith, prevent the mil 1 from grounding on the bed plate or floor upon which it maybe located. Inasmuch as it is desirable for a power-limiting reactant-e coil to ofie" considerable reactance on short circuits only, it is usual to provide no core for the coil except an air core which imparts a straight line characteristic. In order that a coil having an iron core and a comparatively low reactance, may possess a straight line characteristic, it is essential to provide a very large core requiring a prohibitive amount of iron. However,, it may be more economical to provide an iron core for a reactance coil of comparatively high reactanoe.

I prefer to provide a coil comprising several bare copper strands-which are connected in multiple to furnish adequate cross sectional area for the passage therethrough of the load current without undue resistance. The use of several spaced conductors increases the heat-radiating capacity and de-' creases, to some extent, the internal circulating currents, thereby increasing the oper ating efliciency of the coil. In order to further decrease the losses occasioned by the internal circulating currents resultingnfrom unequal potentials existin between the various conductors, I provi e a new form of winding which insures a minimum amount of electrical losses in the conductors comprisin the coils.

In t e drawing, I have shown the windin as consisting of three'conductors connect in multiple, but it will be understood that any convenient number of conductors ma be used and that what is hereinafter saidre ative to the three conductors may be applied also with equal efiectiveness to any number of conductors.

Referring to Fig. 2, three strands 12, 13 and 14, which are connected to their respective binding posts 8, are spirally wound to form the flat coil section 2, substantially as shown. The points 15, 15' and 15", where the conductors initially engage the radial bars 5, are equally spaced from one another on the ifiner periphery of the coil, the bars 5 being provided with recesses or notches 4 with which the said conductors enga e and which are spaced apart to permit 0 thorough ventilation of the conductors.

T 0 illustrate my method of winding each of the coil layers 2, I will describe how the conductors 12, 13 and 14 are wound when a total of three conductors are connected in multiple. The conductor 12, extending from one of thebinding posts 8, engages the innermost recess formed in a radial bar 16 at 15. Continuing in the corresponding recess in a bar 16", the conductor 12 is then stepped radially outward to the second recess formed in a radial bar 17, while the conductor 13 initially engages the innermost recess of the same bar at 15. The conductors 12 and 13 engage the corresponding recesses in bar 17 but, on reaching a bar 18, the former conductor engages the third recess thereof and the latter conductor engages the second recess, while the conductor 14 engages the innermost recess at 15". The three conductors 12, 13 and 14 continue to engage the corresponding recesses in bar 18, but, on arriving at t e bar 16, the conductor 14 is stepped outwardly to the second recess, the

conductor 13 to the third recess, and the conductor 12 to the fourth recess, the innermost or first recess having been previously engaged To-illustrate, the conductors 12, 13 and 14 are severally wound-to form independent spirals which alternate in position with one another in each layer or section of the coil. The conductors are al'soarranged so that each may, in its turn, individually occupy peripheral s aces of equal magnitude at equal radial istances from the center of the coil. In this manner, equal quantities of the symmetrically distributed ma generated by the coil may sim taneously cut the several conductors of each layer or section of the coil. A

It is obvious, from the foregoing description that each of the three conductors occupies the innermost position in this layer for, one-third of the periphery. As the winding operation is continued and the first layer is nearing completion,- the conductor 12, after it engages the outermost recess in the bar 18, is stepped downwardly to engage the corresponding recess in the ar 16 of the coil layer of Fig. 3, which layer is immediately adjacent to the top layer of Fig. 2. Similarly, the conductors 13 and 14 successively occupy the outermost notches in the proper radial bars 5 of the second layer and, as shown in Fig. 3, all the conductors are wound to progress inwardly toward the center ,of the' coil. When this coil layer is completed, the conductors are stepped to a third coil layer in which they are again wound similarly to those shown in Fig. 2. This mode of winding is continued until a sufficient number of coil layers have been wound in order to insure adequate reactancc'to the current-limiting coil. it is apparcnt that, when sullicicn't la yers have been wound, the conductors will be extended to terminal binding posts 8, mounted at the bottom of the core structure, as shown in Fig. 1. i

Inasmuch as the conductors 12, 13 and 14 occup equal lwrlpliernl's'pnces in each mmvolution of every layer of the coil, each of the conductorsis simultaneously cut by the same total number of lines of force, thus precluding the ex'istciice of unequal potentials between thevarious conductors. In this manner, the llow of internal circulating currents is'eliminated, thereby effecting a substantial increase in the operating elliciency of my coil over that of cu rrentdimiting coils heretofore constructed.

' In Figs. 4 and 5,1 have shown, somewhat diagrammatically, another currentdimiting reactancc coil in which the internal circulat' ing currents are eliminated by so arranging the conductors relative .to the magnetic lield generated'by the coil that each of the conductors may be out 59; substantially the same total number of lines of force during each currentpulsation.

Fig. 4 is a development of the outer layer of my coil which comprises a plurality of concentric-layers, as shown in Fig. 5, the total number of layers which constitute the completed coil being dependent upon the value of thcreactanoe desired therein.

I have shown three cohductors 19, 20 and 21 connected in parallel, but, as mentioned abovenny convenient number ofconductors may be used and, obviously, what may be said herein relative to the three conductors willifertwith equal ellectiveness to the.

x-i s u; i er jp nd g s -,*-.Longi'tu dinally extending bars 2?. are provided :with'notches 23 which engage the condnctorsi ithcibarsand the notches therein ibeingl spaccd'apart to nermitof thorough en tilation'of the coil. The bars 24:,- 25 and 26; whichtnark the points of transition for thc'condnctnrs 19-20-21, are spaced equally around the periphery of each. coil layer, as indicated in the development of Fig. 4.

@Tn'this modification of my coil, the condoctors are stepped successively downwardly or upwardly into the proper notches 23 in-a manner similar to that of stepping the conductors of Figs. 2 and 3 alternately outward] y-or inwardly in the success-ire layen; as the irindingcpenition progresses. W'hru one of the concentric layers of the coil is completed, the conductors are wound to form the next layer and progress either upwardly or downwardly, the direction of windin; being opposite to that of the layer immediately preceding.

-'l'hc o je t of thus winding the-coi is to of superposed spirals consist ng-p a tors electrically conncctedfin inultiplc'jpnd 'of conductors clectricallyconn rately occupying substanti I y eqnnlkgcriphcomprisim each of the ayers' so position each of the conductors comprising the concentric layers in identical magnetic liclds that the conductors will be simultaneously cut by equal quantities of magnetic flux. lhis.condition precludes the 70 new of internal circulating currents occasioned by the conductors 19-20-21, which are connected in parallel relation, having unequal potentials generated therein.

In Figs. 7 and S, I have shown diagramlunticnlly tn'u electrical distributing systemsemploying reactance coils 27 to protect high capacity geucmtors 28 which feed into the main buses 29. The feeders furnish power to apparatus havinq a high power. factor, 6 such as rotary converters 30, to apparatus having a low power factor, such'as an in duction motor 31, and to a synchronous ma chine 32. Referring to Fig.-7,,thc powervlimiting reactance' coils 21 Jia 35'; the generator leads previous to r: 1" connected to the busesiQfi-whileein Fig- 8, power-limiting rcactanca -rcoils 27-Qirdfi1i sorted between the fccderllines and the buses 29. "The aforementioned SIS-"g terns of employing power-limiting reactants l coils are now extensively used, the adrantages and disadvantages ofench-systein being the determining factorforils adoption" in the particular power installation. be made. i While-I have herein shownfand dwibed" several embodiments of my inventioxy'itwill be understood by those inmhofartfi that various modificationsmay mado'fion without departing from the spirit andscopc of my invention. l

1. A'reactance coil compfising'nkplurahty conduc severally occupying spaces of equal magnitude; tlons of the spirals. w l

' 2. Areactance coil comprising a allcl and sevcrallywoundfiili 'theffoi'in'fo spirals, the conductors occup ing.'s:paratc r peripheral spaces of substanti y cqn mag; nitude at equal distancis-from thccenterot 15 the coil. 7 v 1-1,. 3. A roactance coil comprising}; plurah 7 1- of spaced conductors electrioa p in parallel the snidconductors: I ally wound in the fornrofs' imls andsepv' 12o oral s ideas at ugualdistancesfrom 7 v tcr o the coil, :1. pluralityof such irals forming t m coil. 12:

4. 'A reactancc coil comprising a lurahty of conductors electrically connect in a!'- nllel and severally wound in the form 0 independent splrals that are superposed upon one another, said conductorsbeing so disposed relative to one another as to be simultaneously cut by equal quantities of magnetic flux.

5. A renctance coil comprising a plurality of conductors electrically connected in parallel and severally wound in the form of independent spirals, said conductors being so disposed that substantially' equal segments of the independent spirals are separately cut by magnetic fields of equal intensity.

6. A reactance coil comprising a plurality of substantially concentric layers consisting of conductors electrically connected in multiple and severally occupying separate peripheral spaces of substantially equal magnitude'upon circumferences formed by intersecting planes that are perpendicular to the axis of said coil.

7. A reactance coil comprising a lurality of interconnected sections each of which consists of n conductors electrically connected in multiple relationship and severally wound in side-by-side spiral formations which are 0 offset angularly displaced with respect to one another in each of said sections whereby the lengths of each of the conductors forming the spirals of each section are equal to one another.

8. A reactunce coil comprising a plurality of interconnected sections each of which consists of n conductors electrically connected in multiple relationship and severally wound to form n spiral formations per section, the convolutions of the several spirals of each section being positioned alternately with respect to one another and the spirals being 360 'n another in each of said sections.

9. A reactance coil comprising a lurality of conductors electrically connect in parallel and severally wound in the form of super osecl spirals and occupying sepnrato perip eral spaces of substantially equal magnitude at equal distances from the center of the coil.

In testimony whereof, I have hereunto subscribed my name this 28th day of Jan. 1914.

angularly displaced with respect to one JOHN'F. PETERS.

Witnesses:

J. P. ONEAL,

- B. B. Hmns. 

